Telephone Switch Timeline

A timeline of the development & history of telephone switching systems from the past to the present


Telephone Switch Development & History Timeline

1876 - Alexander Graham Bell files patent on the modern telephone

1891 - Step-by-Step (Strowger) Switch was patented by Almon Strowger

1892 - First commercial Step-by-Step switch exchange opens in La Porte, IN on November 3rd. The system is provided by the Automatic Electric Company under Strowger patents.

1919 - November 8th, the first Step by Step switch was installed in the Bell system (not inherited due to purchase of telephone companies with existing switches) is brought into service in Norfolk, VA. This exchange is installed by the Automatic Electric Company of Chicago for the Bell System.

1920 - First Western Electric Panel switch installed in Omaha, NE.

1921 - On July 30, the first Step-by-Step switch made by Western Electric is installed in Dallas.

1928 - On May 27th, the first 350A Community Dial Office in the Bell System is opened in Arcadia, California.

1938 - The first #1 Crossbar switch is installed at the Troy Avenue central office in Brooklyn, NY.

1941 - First installation of Crossbar Tandem (XBT) regional tandem switch.

1943 - The first #4 Crossbar toll tandem switch was installed in Philadelphia, PA.

1948 - On July 11th, the first #5 Crossbar switch was installed at Media, PA.

1951 - The first 356A Community Dial Office (75 lines) is installed in Roberts, Idaho on February 15th. 

1951 - On November 10, the trial of customer-dialed DDD (Direct Distance Dialing) begins at Englewood, N.J. (#5 Crossbar)

1953 - Western Electric develops the Card Translation System for the #4 Crossbar toll tandem switch.

1955 - On March 18th, AT&T marks the announcement of the initial trial installation of electronic switching for Morris, IL.

1956 - First installation of North Electric NX-1 Crossbar switch in Seymour, IN.

1960 - November 1st sees the first field trial of Touch Tone calling undertaken in Findlay, OH. (#5 Crossbar)

1960 - On November 17th, AT&T conducts customer trials begin of the world's first electronic telephone switch in Morris, IL utilizing cold-cathode vacuum tubes.

1963 - AT&T introduces commercial use of Touch Tone service in Carnegie and Greensburg, PA (Modified #5 Crossbar).

1965 - On May 30th, Western Electric installs the first #1ESS electronic telephone switching system is installed in Succasunna, NJ. Initially, only 200 of the 4,300 subscribers take advantage of the new Custom Calling Services such as third-way calling & speed dialing. The #1ESS is transistor based and is used as a local metropolitan switch allowing for 65,000 lines and 16,000 trunks.

1966 - On June 15th, AT&T demonstrates first International Direct Distance Dialing (IDDD) utilizing 10 digits on a modified #5 Crossbar switch (no other #5 Crossbar switches were used for IDDD).

1968 - The #1ESS is modified for use as both a local metropolitan switch and local tandem switch.

1969 - Western Electric introduces Electronic Translator System (ETS) for #4 Crossbar toll tandem switches.

1970 - March 1st sees the introduction of international DDD from London to New York City (#1ESS switch with modified #4 Crossbar switch that served as International Gateway)

1970 - Western Electric develops the #2ESS switch for local suburban has 30,000 lines and trunks together.

1972 - Automatic Electric introduces the #1EAX electronic switching system.  Last installation of Western Electric #5 Crossbar switch in Spencer, OK.

1974 - The #1ESS is adapted to allow 2-wire toll switching.

1976  - AT&T installs its first #4ESS full digital toll tandem switch in Chicago, IL as a large 4-wire toll tandem for use of 100,000 trunks. Last installation of #4 Crossbar toll tandem switch.

1976 - The 1A processor is introduced, upgrading the #1ESS switch to #1AESS  for large metropolitan local use has 90,000 lines and 32,000 trunks.

1976 - Northern Telecom (Nortel) demonstrates the DMS-10 at the Digital World expo in February.

1976 - Vidar (later TRW-Vidar) demonstrates their ITS-5 local central office digital switch.

1976 - Western Electric develops the #2BESS for local suburban use has 30,000 lines and trunks together.

1976 - Western Electric develops the #3ESS for local rural use has 5,800 lines and trunks together.

1977 - Stromberg-Carlson conducts field trial and installation of first production switch of their Digital Central Office (DCO) in Richmond Hill, GA.

1977 - Siemens of Germany begins development of their EWSD digital switch.

1977 - First production Northern Telecom DMS-10 installed in Fort White, FL in October.

1977 - The #1AESS is adapted for using 4-wire toll.

1978 - Vidar installs first commercial production ITS-4/5 switch.

1978 - Automatic Electric develops the GTD-3 (#3EAX) full digital local office switch.

1979 - Western Electric develops the #10A RSS (remote switching system) for local small rural areas with 2,000 lines.

1979 - The #1AESS is adapted for local, tandem, and toll capability.

1979 - Northern Telecom installs first production DMS-100 local central office switch.

1982 - Western Electric installs the first #5ESS local central office switch for local rural to large metropolitan areas with tandem and toll capabilities has from 150,000 lines and 50,000 trunks to 0 lines and 60,000 trunks.

1982 - Automatic Electric develops the GTD-5 (#5EAX) digital local office switch. 

1984 - Court ordered divestiture breaks up AT&T. Local operating companies form seven Regional Bell Operating Companies (RBOCs). Western Electric/Bell Labs is absorbed into AT&T.

1989 - Automatic Electric & AT&T join forces to form AGCS.

1990 - The telephone switch division of Stromberg-Carlson is sold to Siemens.

1996 - AT&T spins off hardware technology development into Lucent Technologies. AGCS becomes part of Lucent.

1999 - Lucent installs last #4ESS switch in Atlanta, GA. A total of 145 #4ESS machines were installed in the AT&T Long Lines network with several more installed for regional (RBOC) use.

2002 - Last known Step-by-Step switch in North American public switched network is replaced with a digital (DMS-10) switch in Nantes, QC Canada. This switch was probably the last fully electro-mechanical switch in the North American PSTN.

2003 - Sprint Local (EMBARQ) begins replacement of traditional Nortel DMS-100 digital time-domain circuit-switched telephone switches with new Nortel Communications Server packet-based softswitches.

2005 - Last known group of Vidar switches in the US are replaced with CopperCom softswitches in Linn Grove, Peterson and Rembrandt, IA.

2005 - AT&T merges with SBC (former Southwestern Bell Company, an RBOC spun off from AT&T in 1984) to form "the new at&t".

2006 - The local landline divison of Sprint is spun off as EMBARQ.

2006 - BellSouth merges with the "new at&t". BellSouth was the last "Baby Bell" to keep its original name from the 1984 breakup of the old AT&T.

2006 - Lucent is sold to French telephone equipment maker Alcatel to form Alcatel-Lucent.

2006 - Windstream is formed from Valor telecom and the former wireline division of Alltel.

2007 - With all of Cingular under one owner, the name is changed to at&t Mobility.

2009 - EMBARQ and CenturyTel merge

2009 - Centennial Wireless merges with at&t Mobility

2009 - Alltel Wireless merges with Verizon Wireless

2010 - CenturyLink buys Qwest and becomes largest PSTN company in terms of square mileage.


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